Infants' Processing of Actions and Goals: A Social Neuroscience Approach. How do we come to understand the actions of other people? What neural systems are associated with understanding others, and how do these systems develop? Addressing these critical questions has far- reaching implications for understanding both typical and atypical human development. Much current interest in this area concerns whether the neural systems involved in infants' own production of actions are also active during the perception of similar actions by others. Debate in this area has centered on the nature and function of this putative shared activation in terms of its role in early action understanding. Until recently, such discussions have largely been speculative, calling for more data, rather than being able to summarize empirical results. Studies from our own and others' laboratories have begun to modify this picture through the application of electroencephalographic (EEG) techniques to the study of intermodal links between perception and production in infants' action processing. Recent work in this area has focused on a particular measure, the desynchronization of the sensor motor mu rhythm during action observation by infants. However, it remains very difficult to say exactly what is being reflected by changes in the mu rhythm while infants are viewing other people's actions. In this proposal we take a highly innovative, integrative approach to this issue by tackling a key question that needs to be addressed in order to move the field forward: What specific aspects of observed actions is the infant mu rhythm response sensitive to? In the proposed work we will make significant inroads into this critical problem by connecting recent findings from neuroscience with the extant literature on infant imitation, leading to a potentially powerful confluence of subfields within developmental science. The proposed work is a step toward building bridges between the emerging infant neuroscience work and the corpus of behavioral evidence showing the flexibility of human imitation.